A conventional fuel injection device mounting structure in an intake structure of an internal combustion engine is known. A fuel injection device is installed in a cylinder head so as to face a generally U-bent intake passage. A fuel injection orifice in the fuel injection device thus installed in the cylinder head in a facing relation to the intake passage is oriented toward an intake port, which is an opening of the intake passage in a combustion chamber. Fuel injection is aimed directly at a valve head of an intake valve in a closed state of the intake port. See, for example, FIG. 9 of Japanese Patent Laid-open No. 2001-138975.
A fuel injection device 014 of an internal combustion engine in a motorcycle configured as disclosed in Japanese Patent Laid-open No. 2001-138975 is illustrated in FIG. 12. The fuel injection device 014 is installed in a cylinder head 01 in such a manner that a fuel injection orifice 014a thereof faces a curved top portion 012d of a generally U-bent intake passage 012 formed in the cylinder head 01. The fuel injection device 014 is installed in the curved top portion 012d in such a manner that the axis thereof intersects the curved top portion 012d at a predetermined angle.
Once the fuel injection device 014 is installed in accordance with such a disposing structure, the injection of fuel is oriented toward an opening of the intake passage 012 in a combustion chamber 011, that is, toward an intake port 012a. To be more exact, the injection of fuel is aimed directly at a portion corresponding to the head of an intake valve 012b in a state in which the valve closes the intake port 012a. 
However, this injection of fuel aiming directly at the head of the intake valve in the intake port in the installed state of the fuel injection device can be disadvantageous for the following reasons. In an internal combustion engine having an overlap of opening and closing of valves, that is, in an engine wherein valves perform opening and closing motions such that an exhaust valve has not yet closed an exhaust port completely when an intake valve begins to open an intake port, injected fuel blows together with air toward the exhaust port simultaneously with opening of the intake port. A portion of the injected fuel is discharged together with exhaust gas through an exhaust passage from the exhaust port.
Such a portion of the injected fuel discharged together with exhaust gas through the exhaust passage results in an increase in the amount of HC contained in the exhaust gas. It is necessary to install a secondary air introducing device and an exhaust gas treating device such as CAT to prevent such an increase in the amount of HC contained in the exhaust gas and for decreasing the amount of HC. Post-treatment of the exhaust gas with use of these devices is therefore important.
One countermeasure for preventing such blowing of injected fuel may be the adoption of means performing fuel injection after the completion of an overlapped state of both intake and exhaust valves. However, since the adoption of such means retards the fuel injection timing by the fuel injection device, the injection of fuel is not completed within the opening time of the intake port by the intake valve. That is, the injection of fuel by the fuel injection device is not completed until complete closure of the intake port by the intake valve.